Magneto-optical recording medium having a plurality of ferromagnetic thin layers

ABSTRACT

A magneto-optical device including a substrate which is transparent to light in a visible spectrum region and, a plurality of ferromagnetic layers arranged thereon, each ferromagnetic layer preferably having a width ranging from in an inclusive range of 5 to through 100 nanometers and a thickness ranging from in an inclusive range of 0.1 to through 5 microns. The, wherein said ferromagnetic layers are parallel to each other and separated by a distance ranging from in an inclusive range of 0.2 to through 2 microns. The ferromagnetic layers are arranged preferably on the side walls of grooves formed parallel to each other in the transparent substrate.

CROSS-REFERENCES TO RELATED APPLICATION

This application claims priority to Japanese Application No. 9-117626,filed Apr. 21 1997 and Japanese Application No. 10-103612, filed Mar.31, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magneto-optical device which ishighly transparent and capable of repeatedly carrying out recording andreading operations including erasing through magnetic heads. Themagneto-optical device may also be used in a polarizer, in a displaydevice for displaying picture images by applying a magnetic field andilluminating light, in a spatial optical modulator and in magnetic fieldsensor.

2. Description of the Related Art

When linearly polarized light is incident on a magnetized material withits propagation direction parallel to the direction of the magnetizationof the magnetized material, the plane of the linear polarization isrotated by the magnetic field, which is well known as the Faradayeffect. Utilizing magnetic materials having a relatively largecoefficient of the effect, several devices have been fabricated such asmagnetic recording media and spatial optical modulator.

As examples of such devices, there disclosed are magnetic recordingmedia (1) using yttrium rare-earth iron garnet and its derivativedisclosed in Japanese Laid-Open Patent Application 56-15125/1981, (2)using hexagonal ferrite in Japanese Laid-Open Patent Application61-89605/1986, (3) a coated magnetic recording medium using yttrium irongarnet particulates in Japanese Laid-Open Patent Application62-119758/1987 and (4) another coated magnetic recording medium usingrare-earth iron garnet particulates in Japanese Laid-Open PatentApplication 4-132029/1992.

These magnetic recording media each generally consist of thin layers ofeither magnetic material or its particulates disposed on a substrate.

Although these media in general have excellent capability of writing andreading various information data, their use has been rather limited tothose applications mentioned above. In other words, they are not soadvantageous for other applications such as, for example, informationdisplay.

SUMMARY OF THE INVENTION

It is an object of the present invention, therefore, to provide amagneto-optical device which is capable of carrying out recording andreading operations including erasing through magnetic heads and whichmay also be utilized in a polarizer, in a display device for visuallydisplaying picture images by applying magnetic field and illuminatinglight.

A further object of the present invention is to provide amagneto-optical device which has an excellent response capability to theintensity of applied magnetic field and is therefore capable of visuallydisplaying even slight differences in display contrast caused by minutedifferences in applied magnetic field strengths.

In a further object of the present invention there is provided amagneto-optical device which may also be used in a spatial opticalmodulator and in a magnetic field sensor.

According to the present invention, a magneto-optical device is firstlyprovided, including a substrate and a plurality of thin layers offerromagnetic material disposed on the substrate. The substrate ispreferably transparent in the visible spectral region. The thin layersof ferromagnetic material each preferably have a width of from 5 to 100nanometers and a thickness of from 0.1 to 5 microns and the plurality ofthe thin layers each being parallel with one another with a spacing offrom 0.2 to 2 microns.

Secondly, a magneto-optical device is provided, characterized in thatthe thin layers of ferromagnetic material of the magneto-optical deviceare preferably disposed on side wall portions of a plurality of concavegrooves provided parallel with one another on the substrate which istransparent in the visible spectral region.

Thirdly, a magneto-optical device is provided, characterized in thatside wall portions of the magneto-optical device for the thin layers offerromagnetic material to be disposed are preferably perpendicular tothe surface plane of the substrate.

Fourthly, a magneto-optical device is provided, characterized in that atleast one reflecting layer is further provided on one of the faces ofthe substrate of the magneto-optical device

Fifthly, a magneto-optical device is provided, characterized in that ananti-reflective layer is further provided on the back side of thesubstrate from the reflecting layer.

Sixthly, a magneto-optical device is provided, characterized in that thethin layers of ferromagnetic material are preferably electricallyconductive.

Seventhly, a magneto-optical device is provided, characterized in thatthe thin layers of ferromagnetic material essentially consist ofultra-fine particles of Fe, Co, Ni or alloy thereof, having an averagediameter of from 2 to 20 nanometers.

Eighthly, a magneto-optical device is provided, characterized in that alayer of non-magnetic semiconductive material or metal is furtherprovided in contact with each of the thin layers of ferromagneticmaterial, having the same thickness as that of the thin layers and awidth of from 5 to 10 nanometers.

As described earlier, the magneto-optical device of the presentinvention includes a substrate which is transparent in the visiblespectral region and a plurality of thin layers of ferromagnetic materialdisposed thereon, each of the thin layers having a width of from 5 to100 nanometers and a thickness of from 0.1 to 5 microns, being parallelwith one another with a spacing of from 0.2 to 2 microns.

The magneto-optical device is therefore capable of achieving both highlight transmittance and polarizability by the magneto-optical effect atthe same time, to thereby result in a high contrast in transmittancevalues for visible light, between magnetized and non-magnetizedportions. In addition, since these characteristics of the presentmagneto-optical device enables for picture images to be recorded onlarge area display panels, the magneto-optical device may be used indisplay applications. Furthermore, since the device has an excellentresponse characteristics to the intensity of applied magnetic fields,the device is capable of visually displaying even slight differences indisplay contrast caused by minute differences in applied magnetic fieldstrengths.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is an enlarged schematic cross-sectional view of amagneto-optical device according to one embodiment of the presentinvention.

FIG. 2 is an enlarged schematic top view of the magneto-optical deviceof FIG. 1.

FIG. 3 is an enlarged schematic cross-sectional view of amagneto-optical device according to another embodiment of the presentinvention.

FIG. 4 is an enlarged schematic cross section view of a ferromagneticthin film layer superimposed with non-magnetic semiconductor or metallayers according to the present invention.

FIG. 5a shows a schematic cross-sectional view of the micro magnetichead in accordance with one embodiment of the present invention.

FIG. 5b shows a schematic top-view of the micro magnetic head inaccordance with one embodiment of the present invention.

FIG. 6 is a schematic circuit diagram of one embodiment of themagneto-optical device of the present invention for writing and readingusing a two-dimensional micro magnetic head array.

FIG. 7a is a cross sectional view of a reading head according to thepresent invention.

FIG. 7b is a top view of a reading head according to the presentinvention.

FIG. 8 is a schematic circuit diagram of another embodiment for writingand reading using a one-dimensional micro magnetic head array accordingto the present invention.

FIG. 9 is a cross sectional view of the magneto-optical device of thepresent invention, which illustrates the manifestation of contrast whenthe magneto-optical device of the present invention is used in a displaydevice.

FIG. 10a-h illustrate the fabrication process steps of themagneto-optical device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A magneto-optical device of the present invention has such a basicstructure as to include a substrate which is transparent in the visiblespectral region and a plurality of thin layers of ferromagneticmaterial, having a width of from 5 to 100 nanometers and a thickness offrom 0.1 to 5 microns and being disposed on the substrate parallel withone another with a spacing of from 0.2 to 2 microns.

Experimentation has been carried out by the inventor concerning to thedegree of polarization of the magneto-optical device of the presentinvention.

When a constant area of the surface of a magneto-optical device isilluminated, it has been found that the degree of polarization increaseswith the increase in the height of ferromagnetic layers and also withthe decrease in the distance between the layers, or with the increase inan aspect ratio (i.e., height of ferromagnetic thin layers /distancebetween the layers). During the experimentation the polarizability valueof more than 40% has been achieved.

FIG. 1 is an enlarged cross-sectional view of a magneto-optical devicein accordance with one embodiment of the present invention.

Referring to FIG. 1, on a substrate 1 which is transparent in thevisible spectral region, a plurality of thin layers 4 of ferromagneticmaterial are disposed, having a width M of from 5 to 100 nanometers anda height H of from 0.1 to 5 microns, each being parallel with oneanother with an equal spacing, i.e., L1=L2, of from 0.2 to 2 microns.Furthermore, the thin layers 4 of ferromagnetic material are disposed onside wall portions vertically to the surface plane 2, of a plurality ofconcave grooves 3 previously formed on the substrate on the substrate.

FIG. 2 is an enlarged top view of the magneto-optical device of FIG. 1.

Referring to FIG. 2, on the surface of the substrate 1 which istransparent in the visible spectral region, a plurality of thin layers 4of ferromagnetic material are disposed on side wall portionsperpendicular to the surface plane 2, of a plurality of concave grooves3.

FIG. 3 is an enlarged (cross-sectional view of a magneto-optical devicein accordance with another embodiment of the present invention.

Referring to FIG. 3, on a substrate 1 which is transparent in thevisible spectral region, a plurality of thin layers 4 of ferromagneticmaterial are disposed, having a width M of from 5 to 100 nanometers anda height H of from 0.1 to 5 microns, each being parallel with oneanother with an equal spacing, i.e., L1=L2, of from 0.2 to 2 microns.

The magneto-optical device further comprises a reflecting layer 6provided on one of the faces of the substrate of the magneto-opticaldevice. An anti-reflective layer 7 is further provided on the back sideof the substrate 1 against the reflecting layer 6.

The reflecting layer 6 may be provided by pasting a reflecting layerwhich is previously disposed on one of the faces of another substrate1A, onto the back side of the substrate 1 against the substrate 1.

It is noted in FIGS. 1 and 3 that the numeral 5 represents a pluralityof thin layers of ferromagnetic material, which possess, in fact, bothpolarizing and magnetic capabilities at the same time.

The width M of the ferromagnetic layer 4 is preferably from 5 to 100nanometers. For the width of less than 5 nanometers, the reduction inthe magneto-optical effect of the device results, thereby making itdifficult for the magneto-optical device be used in a display. Bycontrast, for the width of greater than 100 nanometers, the degree ofpolarizability in the visible spectral region decreases and thetransmittance also decreases down to 50% or less, thereby making it alsodifficult for the magneto-optical device to be used in a display.

The height H of the ferromagnetic layer 4 is preferably from 0.1 to 5micron. The magnitude of the rotation of the plane of the linearpolarization by the magneto-optical effect is related to this height,thereby facilitating more versatile designing for desirable displaycontrasts of the magneto-optical device

For the layer height of less than 0.1 micron, polarization andmagnetization effects such as expected to continuous ferromagneticlayers only becomes evident. By contrast, transmittance decreases forthe height of greater than 5 microns, thereby making it also difficultfor the magneto-optical device be used in a display.

The spacing L between ferromagnetic layers 4 is preferably from 0.2 to 2microns. For the spacing of less than 0.2 micron, transmittance and thedegree of polarizability decrease, thereby making it difficult for themagneto-optical device be used in a display.

By contrast, for the spacing of greater than 2 microns, the polarizationeffect such as expected to continuous ferromagnetic layers only becomesdominant, thereby making it difficult for the magneto-optical device beused in a display or polarizing device.

Although, as described earlier, the plurality of thin layers of theferromagnetic material are preferably provided on the side wall portionsvertically to the surface plane of the grooves with a width of from 5 to100 microns and a height of from 0.1 to 5 microns, slight tilt and/orbent of the thin layers are found not to substantially affect to devicecharacteristics.

In place of hollow grooves, the grooves 3 provided on the substrate mayalso be formed in such a manner that the hollow portions are filled withmaterial which is transparent and has a refractive index different fromthat of the substrate. Examples of such transparent materials areillustrated in Table 1. When the hollow portions are filled withmaterial with the same refractive index as that of the substrate,neither light diffraction due to interference nor appreciablemagneto-optical effect is observed.

Examples of suitable materials for the transparent substrate of themagneto-optical device of the present invention include inorganicmaterials such as quartz glass, sapphire, crystallized glass, Pyrexglass, Al₂O₃, MgO, BeO, ZrO₂, Y₂O₃, ThO₃, GaO, and GGG (GadoliniumGallium garnet); and transparent films of plastics, such as MMM (methylmethacrylate), PMMA (polymethyl methacrylate), polycarbonate,polypropylene, acrylic resins, styrene resins, ABS(acrylonitrilebutadiene styrene) resins, polyallylate, polystyrene, polysulphone,polyether sulphone, epoxy resin, poly-4-methylpentene-1, fluorinatedpolyimide, fluorine resins, fluororesin, phenoxyresin, polyolefin resinsand nylon resins.

These plastic films are advantageous for the device fabrication due toits light weight and flexibility.

The thickness of the transparent substrate suitable for the device ispreferably from 50 to 500 microns. As the thickness of the substratedecreases, the substrate becomes more suitable for recording due toreduced distances between a magnetic head and polarization and/ormagnetization layer 5. By contrast, for the thickness of greater than500 microns of the substrate, it also becomes possible to record with amagnetic head from the backside of the device against the reflectinglayer 6 in FIG. 3.

As the materials for ferromagnetic thin layer 4 suitable for recordingof the present invention, it is preferable for these materials toexhibit high magneto-optical effect, to have magnetic anisotropy in theplane of the ferromagnetic layer and a coercive force value of from 200to 2000 Oe. In addition, since the polarization and magnetization layer5 is also capable of acting in a polarizing device, it is essential forthe materials of the ferromagnetic thin layers to be electricallyconductive to thereby give rise to the transfer of electrons under theelectric field of light.

Accordingly, when the ferromagnetic layer consists of insulatingmaterials such as, for example, Fe₂O₃, CoFe₂O₄,Bi₂DyFe_(3.8)Al_(1.2)O₁₂, it is preferable for non-magneticsemiconductor or metal layer be superposed with the insulatingmaterials, to thereby form electron movable layers.

Because of the increase in light absorption with the increase in thethickness of the superimposed layer, the thickness is preferable to beas small as possible for the semiconducting layer. Furthermore, it isalso preferable to form the ferromagnetic layers with conductivematerials so as to secure the conductive property even withoutadditional conductive layer.

A ferromagnetic thin layer superimposed with non-magnetic semiconductoror metal layers is exemplified in an enlarged cross sectional view ofFIG. 4.

The superposition of the non-magnetic semiconductor or metal layer 8with the ferromagnetic thin oxide layer 4A can be accomplished either byproviding the non-magnetic semiconductor or metal layer 8 on theferromagnetic thin oxide layer 4A previously disposed on the side wallsof the grooves, as shown in FIG. 4a, or by providing the ferromagneticthin oxide layer 4A on the non-magnetic semiconductor or metal layers 8previously disposed on the side walls of the grooves, as shown in FIG.4b.

The ferromagnetic layer is preferably be highly transparent. Examples ofmaterials for ferromagnetic thin layers include conventional transparentferromagnetic materials. Therefore, it is preferably for the materialsto be transparent and to have a large Faraday effect and itscoefficient.

Examples of the ferromagnetic thin layers of abovementioned materialsinclude thin layers comprising ultrafine particles of ferromagneticmetals such as, for example, iron (Fe), cobalt (Co), nickel (Ni) andalloys thereof, having an average diameter of from 2 to 20 nanometers.

These ferromagnetic layers may be formed by evaporation method, and morepreferably by evaporation under rare gas atmosphere mixed with a smallamount of air (e.g., several 100 m-Torr) in the evaporation chamber.Through this evaporation process step, the ferromagnetic layer generallyinclude oxygen, carbon and other elements in addition to theabove-mentioned principal metallic components.

Although metallic elements such as, for example, iron, cobalt and nickelexhibit large magneto-optical effect, these materials by themselves aregenerally difficult to be used as the present ferromagnetic layermaterials. This difficulty can preferably be overcome in the presentinvention by the formation of thin layers including ultra-fine particlesof the above metals, thereby realizing magneto-optical characteristicslarge enough for the ferromagnetic layer application of the presentinvention.

In addition, by controlling the size of, and the distance between theultra-fine particles formed, respectively, its coercive force value andmagnetic anisotropy in the plane of the ferromagnetic layer can beadjusted.

Because of the inclusion of the metallic ultra-fine particles,furthermore, the present ferromagnetic thin layers are highlyconductive, to thereby be preferably used by themselves as theferromagnetic layer materials for the polarization and magnetizationlayer 5, which may be used in a polarizing device.

In addition to the aforementioned examples, materials suitable forferromagnetic thin layers of the present invention further includeoxides such as rare-earth iron garnet, cobalt ferrite and bariumferrite; materials having large birefringence values, such as FeBO₃,FeF₃, YFeO₃, and NdFeO₃; transparent magnetic materials such as MnBi,MnCuBi and PtCo.

Since the magneto-optical effect utilized in the present invention ismost effective in the parallel configuration between the directions oflight propagation and the magnetic spin orientation, the ferromagneticmaterials are preferably disposed so as to have a magnetic anisotropy inthe plane of the ferromagnetic layer.

The ferromagnetic thin layers may preferably be formed by PVD (physicalvapor deposition) or CVD (chemical vapor deposition) method such assputtering, evaporation, and MBE (molecular beam epitaxy), and platingmethod, for example.

As the materials for anti-reflection layer suitable for themagneto-optical device of the present invention, it is preferable forthese materials to have high reflectivity in a certain visible spectralregion.

Examples for the above materials includes Cu, Al, Ag, Au, Pt, Rh,TeO_(x), TeC, SeAs, TeAs, TiN, TaN and CrN. Using these materials, theabove anti-reflective layer may be formed through the methods such asevaporation, sputtering and ion plating, preferably to a thickness offrom 50 to 100 nm. In addition, examples of the anti-reflection layermay further include multiple alternating layers of oxides such as, forexample, SiO₂ and TiO₂, and of metals; a slant viewing type ofreflecting plate, and a hologram reflecting plate (Holobrite fromPolaroid Japan Co).

In order to improve light transmittance, and to prevent chemicalcorrosion, and weathering by light irradiation, of the magneto-opticaldevice, an anti-reflective layer is further provided on the back side ofthe device against the reflecting layer, which is especially preferablewhen the device is used in a display panel. The anti-reflection layer ofthe present invention may preferably be disposed through evaporationmethod using materials such as shown in table 1, for example.

TABLE 1 Refractive Index and Transparent Spectral Region of Thin LayerMaterials for Anti-Reflective Layer Refractive Index Transparent(Wavelength in Spectral Thin Layer Material nanometers) Region n < 1.5calcium fluoride (CaF₂) 1.23~1.26 (546) 150 nm~12 μm sodium fluoride(NaF) 1.34 (550) 250 nm~14 μm cryolite (Na₃AlF₆) 1.35 (550) <200 nm~14μm   lithium fluoride (LiF) 1.36~1.37 (546) 110 nm~7 μm magnesiumfluoride 1.38 (550) 210 nm~10 μm (MgF₂) silicon dioxide (SiO₂)1.46 (500) 200 nm~8 μm  1.5< lanthanum fluoride (LaF₃) 1.59 (550) 220nm~>2 μm n < 2 neodymium fluoride 1.6  (550) 220 nm~>2 μm (NdF₃)aluminum oxide (Al₂O₃) 1.62 (600) cerium fluoride (CeF₃) 1.63 (550) 300nm~>5 μm lead fluoride (PbF₂) 1.75 (550) 240 nm~>20 μm magnesium oxide(MgO) 1.75 (500) thorium oxide (ThO₂) 1.8  (550) 250 nm~>2 μm  tin oxide(SnO₂) 1.9  (550) lanthanum oxide (La₂O₃) 1.95 (550) 350 nm~>2 μmsilicon monoxide (SiO) 1.7~2.0  (550) 500 nm~8 μm  2< indium oxide(In₂O₃) 2.0  (500) n < 3 neodymium oxide 2.0  (550) 400 nm~>2 μm (Nd₂O₃)antimony trioxide (Sb₂O₃) 2.40 (546) 300 nm~>1 μm zirconium oxide (ZrO₂)2.1  (550) cerium dioxide (CeO₂) 2.2  (550) 400 nm~10 μm titaniumdioxide (TiO₂) 2.2~2.7  (550) 350 nm~12 μm zinc sulfide (ZnS) 2.35 (550)380 nm~25 μm bismuth oxide (Bi₂O₃) 2.45 (550) zinc selenide (ZnSe) 2.58(633)   600 nm~>15 μm cadmium sulfide (CdS) 2.6  (600) 600 nm~7 μm  3 <n antimony sulfide (Sb₂S₃) 3.0  (589) 500 nm~10 μm cadmium telluride(CdTe) 3.05 (IR) silicon (Si) 3.5   1.1 nm~10 μm germanium (Ge) 4.0   1.7 nm~100 μm tellurium (Te) 4.9  (6 μm)  3.4 nm~20 μm lead telluride(PbTe) 5.5   3.4 nm~30 μm

Although the magneto-optical device of the present invention has apolarizing capability by itself as aforementioned, the device mayfurther be provided with additional polarizing layer to enhance thepolarizing capability.

As the polarizing layer, there may be used conventional polarizing filmsand highly transparent polarizers using beam splitters. The polarizingfilms include a perhalogenated film polarizer, dyestuff polarizer, andmetal layer polarizer. Either one of these polarizers may preferablyused for the magneto-optical device of the present invention. Theperhalogenated film polarizer utilizes iodine as the dichromaticmaterial, to thereby result in useful polarizing characteristicsrelatively independent of light wavelength. Although the dyestuffpolarizers have polarizing characteristics not so good as those of theperhalogenated film polarizers, the former polarizers are more durableagainst heat, light and temperature.

In order to carry out a writing (or recording) operation into thepolarization and magnetization layer of the present magneto-opticaldevice, there is used a magnetic head. Since the magnetic head isoperated by being placed on either the bottom or the top face of thedevice, the writing operation into the polarization and magnetizationlayer can be accomplished without traveling the head at a high speed,which is generally required in the writing operation. This is in muchcontrast to prior art magnetic memory devices such as, for example,magnetic tapes and magnetic disks.

As the magnetic head of the present invention, a magnetic head maypreferably be used, which consists of a plurality of magnetic headsconstructed of a tiny bar of soft magnetic material around which thincopper lines are wound and subsequently arranged in matrix. As themagnetic head array preferably used in the present invention, thepreferable diameters of the tiny bar and thin copper wire areapproximately 100 microns and 20 microns, respectively, and thepreferably distance between the magnetic heads in the matrix isapproximately 50 microns. The wound thin copper lines are a couple ofthin copper lines, and one of which is used for DC for recording, whilethe other is for AC for magnetizing the heads. For the detection ofmagnetic fields, the above wound line for DC may preferably be used.

Besides the above-mentioned magnetic head construction, otherconstructions are also conceivable in the present invention. Forexample, another magnetic head may comprise a core portion of a softmagnetic material formed by plating method with a coil portions formedby the photolithography techniques, and still another magnetic head maycomprise core and coil portions both formed by plating method. The sizeand distance between the magnetic heads and the manner of winding coilsare almost similar to those of the magnetic head array in theabove-mentioned fabrication.

FIGS. 5a and 5b show a micro magnetic head in accordance with oneembodiment of the magneto-optical device of the present invention. FIG.5a is a sectional view of the micro magnetic head and FIG. 5b is a topview of the micro magnetic head. As shown in FIGS. 5a and 5b, atwo-dimensional array of the micro magnetic heads may be fabricated byproviding a plurality of the micro magnetic heads in a matrix fashion.

Referring to FIG. 5, a micro magnetic head 13 is formed, comprising anFe Ni disk-shaped magnet 14 (60 micron in diameter), which is providedin the central portion of the head and surrounded by silicon portions15, having a coil 17 of Au on the silicon portion, which is wound aroundthe top portion of the magnet 14 and is embedded in polyimide resin 16.The coil 17 is then connected to a wiring 19 through a terminal 18.

A plurality of the thus constructed micro magnetic heads 13 may bearranged in a matrix with a distance between the center portions of themicro heads of 120 microns to thereby constitute the array of micromagnetic heads.

The thus prepared micro magnet head array is subsequently provided onthe top face of the magneto-optical device. The write operation into thepolarization and magnetization layer can be carried out in the presentinvention by controlling current supplied to each of the micro magneticheads without traveling a head or at rest in the position of the headrelative to the magneto-optical device.

The magneto-optical device having recorded information is then placedbetween a pair of polarizing films and observed visually under light, tothereby be used in a display panel, for example.

The magneto-optical device of the present invention has an excellentresponse capability to the intensity of applied magnetic field and iscapable of visually displaying even slight differences in displaycontrast caused by minute differences in applied magnetic fieldstrengths.

Besides the aforementioned magnetic head array, a magnetic pen which iscomposed of a cylindrical permanent magnet may also be used in thepresent invention as one of the simplest forms of the magnetic head.

Erasing of image information data recorded in the magneto-optical devicemay be achieved (1) by removing a permanent magnet from, after havingbrought close to, the face of the magneto-optical device, or (2) bymagnetizing the device in the direction opposite to that for theprevious recording.

FIG. 6 illustrates a circuit schematic in accordance with one embodimentof the magneto-optical device of the present invention, which isconfigured in a display panel which is capable of recording and erasinginformation data using the above-mentioned two-dimensional array ofmicro magnetic heads.

Referring to FIG. 6, a magneto-optical device 21 of the presentinvention is provided on a two-dimensional array 20 of micro magneticheads. The two-dimensional micro magnetic head array 20 is constructedof a plurality of the micro magnetic heads of FIG. 5 arranged in matrix.

An address circuit 22 and a driver circuit 23 are further provided,being connected to the micro magnetic head array 20. The address circuit22 is operated so as to select a line of the micro head array and thedriver circuit 23 is to input or to erase information data to each ofthe heads on the selected line. In addition, a controller 24 (PC or PDA)is connected to control writing and erasing operations of informationdata.

Information data to be recorded are input to a CPU 27 of the controller24 through an external memory 25 or a communication line 26 andsubsequently stored in a sequential memory 28. During the writingprocess, the information data are output from the memory 28,sequentially sent through the CPU 27 to the above-mentioned addresscircuit 22 and driver circuit 23, and then input to the magneto-opticaldevice through the micro magnetic head in the two-dimensional micromagnetic head array 20.

Erasing operation of information data may be carried out, for example,by supplying current in the opposite direction to thereby apply magneticfield in the direction opposite to that for the previous recording.

The recording and erasing operations through the magneto-optical deviceof the present invention are therefore achieved without traveling a heador at rest in the position of the head relative to the magneto-opticaldevice. Furthermore, by illuminating visible light upon the recordedmagneto-optical device, the information data may visually be displayedon the magneto-optical device which is now operated as a display panel.

In addition, although inputting the information data intomagneto-optical device can be carried out by the micro magnetic heads ofFIG. 5, the input magnetic data into the magneto-optical device can notbe output by the micro heads, since there is no change either inrelative position between the magneto-optical device and the magneticheads, or in magnetic flux with time.

Accordingly, in order to output the magnetic data, a reading head havingmagnetoresistance effect may preferably be used. FIGS. 7a and 7billustrate an example of the above-mentioned reading head, wherein FIG.7a is a cross sectional view and FIG. 7b is a top view of the readinghead. Referring FIGS. 7a and 7b, the reading head is composed of amagnetoresistance film 29 formed with layered thin film structure of Ni,Co, Fe, Cu and alloys thereof, with a wiring for the resistancemeasurement, which is provided on the substrate 31.

With this reading head, the recorded magnetic data can be output bydetecting the change in resistance of the magnetoresistance layer causedby magnetic flux from the magneto-optical device. Accordingly, atwo-dimensional head array of FIG. 6 is prepared with a plurality ofmagnetic heads arranged in an array matrix, each of which includes onemicro magnetic head of FIG. 5 and one reading head of FIG. 7. By usingthus prepared head array, both of writing and erasing the informationdata can be carried out. The reading of the information data isaccomplished by measuring resistance values of the magneto-resistancefilm with a driver circuit, and then sending the values to CPU andstoring into memory.

FIG. 8 illustrates another embodiment of the system configuration forcarrying out writing and reading information data using aone-dimensional micro magnetic head array 32. CPU 27 drives a motor 33through a control unit of motor driving, to thereby travel themagneto-optical device relative to the micro magnetic head array. Aprecise control of the rotation speed of motor 33 is carried out by adecoder 34 provided with the motor 33.

During the operation with this construction, there are caused somevariations of relative position between the magneto-optical device andmagnetic heads. Therefore, writing and erasing information data are bothachieved using the micro magnetic heads of FIG. 5, without furtherproviding a reading head, which is in contrast to the operation usingthe aforementioned two-dimensional magnetic array.

Although not shown in FIG. 8, another system construction may also befeasible, wherein scanning the magneto-optical device in both ofhorizontal and vertical directions are carried out by using a micromagnetic head array having a relatively few number of magnetic heads andby translating the array in both horizontal and vertical directions, tothereby carry out writing and erasing operations two-dimensionally in amanner similar to that for the conventional printing operation.

FIG. 9 is a cross sectional view of the magneto-optical device of thepresent invention herewith included to illustrate the manifestation ofcontrast when the magneto-optical device is used in a display device.

Referring to FIG. 9, the magneto-optical device comprises a plurality ofpolarization and magnetization layer 5 having the ferromagnetic materialdisposed on the side wall portions perpendicular to the surface plane 2,of a plurality of concave grooves 3 provided on the substrate 1 which istransparent in the visible spectral region, and a reflecting layer 6disposed on the back side of the substrate against the grooves, asdescribed earlier. The ferromagnetic polarization and magnetizationlayer 5 has magnetized and non-magnetized potions 4X and 4Y,respectively.

A couple of light beams 11A and 12A incident on the magneto-opticaldevice are assumed. The light beam 11 A is circularly polarized, and thelight beam turns to linearly polarized light 11B after passing throughthe magnetized portion 4X. The light beam 11B is then reflected by thereflecting layer 6 to be a light beam 11C and passes through themagnetized portion 4X again. Since the plane of the polarization of thelight beam 11C has been rotated from that of 11B and the magnetizedportion 4X acts as a polarizer, the beam 11C can not go through theportion 4X.

In similar manner, the light beam 12A is also circularly polarized andthe light beam turns to linearly polarized light 12B after passingthrough the non-magnetized portion 4Y. The light beam 12C is reflectedback as a beam 12C by the reflecting layer 6, and passes through thenon-magnetized portion 4Y. By contrast to the light beam 11C above,however, the plane of the polarization of the light beam 12C has notbeen rotated by the non-magnetized portion 4Y and is coincident to theplane of the polarization of the magnetization and polarization layer 5.Therefore, the beam 12C can therefore go through the portion 4Y.Accordingly, the light intensity which passes through these portions isdetermined by the magnitude of magnetization of the ferromagneticportion of the ferromagnetic thin layers.

Therefore, the magnetized portions of the ferromagnetic thin layerappears dark, whereas the non-magnetized portions appears light.

Such magneto-optical device as described above may therefore be usedalso in a polarizer. Furthermore, since pattern images may be formed,changed and erased modified on the magneto-optical device at will, thedevice may be used in a display panel even without a back-lightillumination.

Furthermore, the magneto-optical device of the present invention mayalso be used in a spatial modulator. The spatial modulator isfabricated, for example, as follows.

A plurality of solenoids having an inner diameter of approximately 100microns are prepared. These solenoids are then arranged in a matrix andconnected so that each is individually supplied by current formagnetization. The solenoid matrix thus prepared is provided, forexample, directly on the magneto-optical device as shown in FIG. 1, andthis structure is further placed between a pair of polarizers, tothereby be operated as a spatial modulator by controlling the currentsupplied to each of the solenoids. It is noted, since a magnetic spinflop caused by reversing the solenoid current flow takes place withinseveral nanoseconds with this structure, a high speed spatial modulationmay be achieved, to thereby accomplish high speed switching of lightbeams and the use of the present magneto-optical device in a high speedspatial modulator.

In addition, it is also noted, since the magnitude of magneto-opticaleffect depends on that of ferromagnetic thin layer formed on side wallsof the grooves, the magneto-optical device of the present invention mayalso be used in a magnetic field sensor.

The method of fabricating the magneto-optical device of the presentinvention includes the process steps of:

-   -   (1) forming a plurality of substantially linear concave grooves        being parallel with one another on a substrate which is        transparent in the visible spectral region using        photolithography techniques;    -   (2) disposing a thin layer of ferromagnetic material on the        substrate;    -   (3) removing the portions of the ferromagnetic layer on the        substrate using the etching techniques, such that the portions        of the ferromagnetic layer only on side walls of the grooves are        retained, to thereby form stripes of thin layers of        ferromagnetic material;    -   (4) carrying out the formation, and succeeding surface polishing        of a layer of inorganic material, when relevant, which is        further provided, for example, by sputtering process to fill up        the grooves and to thereby obtain a smoothed surface;    -   (5) when relevant, providing a light reflecting layer on one of        faces of the substrate of the magneto-optical device, or pasting        another transparent plate onto one of faces of the substrate,        which is previously provided with a light reflecting layer        thereon; and    -   (6) providing, when relevant, an anti-reflective layer on the        back face of the substrate against the light reflecting layer.

FIG. 10 illustrates fabrication process steps of the magneto-opticaldevice of the present invention.

A layer of a photoresist material 9 is firstly disposed on a transparentsubstrate (a). After providing thereon with a mask having a plurality ofnarrow lines being parallel with one another, the resultant layer isexposed to ultraviolet light, and subsequently wet etched to obtain aphotoresist mask having a pattern of narrow parallel lines, having awidth of 1 ₁ and a spacing of 1 ₂ (b). The transparent substrate is thenetched to thereby a plurality of parallel concave grooves 3 are formed(c), and the mask is removed upon the completion of the etching processstep (d).

Through the above-mentioned steps, a plurality of grooves may be formedwith relative ease, having a large depth vertically to the surface ofthe substrate (up to about 10 microns). In addition, by thephotolithography techniques also, the grooves can be formed havinglinear and smoothed edges.

When a transparent film of plastic material are used as a substrate, athin layer of, for example, Si0 ₂ is disposed on the plastic filmthrough the PVD techniques beforehand, and grooves may be formed on theSiO₂ portions of the substrate.

Subsequently, a thin layer 4 of ferromagnetic material is formed on thegrooved substrate (e). Methods for forming the thin layer preferablyincludes but not limited to PVD, CVD and plating.

The thus formed ferromagnetic layer is then subjected to a sputteringprocess step using Ar ions 10 to remove the portions of theferromagnetic layer on horizontal faces of the grooved substrate (f), tothereby form a plurality of thin layers 4 of ferromagnetic material (g).Although the method for the removal also includes dry and wet methods,the above-mentioned Ar ion sputtering may preferably be used over othermethods, wherein the sputtering is preferably carried out under thereverse biased condition at a negative voltage applied to a substrateelectrode.

A light reflecting layer is formed on a transparent plate 1 A and theresultant structure is pasted on the grooved face of the substrate ofthe magneto-optical device, whereby a magneto-optical device of thepresent invention is fabricated (h).

EXAMPLES

The following examples are provided further to illustrate preferredembodiments of the invention.

EXAMPLE 1

A substrate of quartz was provided having a thickness of 1 mm. On thesurfaces of the substrate, a layer of Cr₂O₃ and thereon a layer of Crwere formed on the substrate, having a total layer thickness of 120nanometers. In addition, a layer of a photoresist material of thepositive type was further provided thereon.

A resultant layer accumulated as above was then subjected to theconventional photolithography techniques for forming a plurality ofnarrow lines being parallel to with one another. During thephotolithography process step, the resultant layer was exposed toultraviolet light using a photoresist mask for narrow parallel lines tobe formed, having L1=L2=1.0 micron (FIG. 1), and subsequently subjectedto a wet etching process step.

The thus formed pattern of the resultant layer on the substrate was usedas a second mask. Using the second mask, the quartz substrate was etchedunder a fluorine gas ambient, to thereby form a plurality of parallelconcave grooves having the depth of 0.65 micron (H in FIG. 1). Upon thecompletion of the etching, the second mask was removed from thesubstrate surface.

Subsequently, a layer of ultra-fine particles of iron was disposed onthe grooved quartz substrate by an evaporation method under gaseousatmosphere without heating the substrate. The gaseous atmosphere wasargon flowing into the evaporation chamber at a rate of 50 sccm and thetotal pressure of 1.0 Pa. The layer of ultra-fine iron particles thusformed was found to have a thickness of approximately 90 nanometers.

The diameter of the iron ultra-fine particles was measured using atransmission electron microscope and found approximately 6 nanometers onthe average. When the iron particle layer was investigated with x-rayphotoelectron spectroscopy (XPS) technique, XPS spectra showed that thelayer consisted of 66% of iron with additional elements such as, oxygen,carbon and nitrogen.

During the above evaporation process, another flat quartz plate wasmounted in the evaporation apparatus adjacent to the above-mentionedquartz substrate, onto which for ultra-fine particles of iron to beevaporated under the identical conditions as those for the groovedquartz substrate. The magnetic characteristics of an iron particle layeron the flat quartz plate were measured to find a coercive force of 32Oe, a squareness ratio of 0.80 and a magnetic anisotropy present in theplane surface of the quartz substrate.

The grooved quartz substrate with the iron particle layer was thensubjected to a sputtering process step as follows. Using a sputteringapparatus which was operated under nitrogen atmosphere and at −400 Voltsapplied to a substrate electrode (i.e., under the reverse biasedcondition), the portions of the iron particle layer previously presenton horizontal faces (2a and 2b in FIG. 1) of the grooved substrate wereremoved, thereby forming a plurality of thin layers of ultra-fineparticles of iron, which were retained only on the vertical portions(the side walls 2 in FIG. 1) of the substrate with the thin layers beingparallel with one another. The layer thus prepared with a plurality ofthin layers of ultra-fine particles of iron are hereinafter referred toas a striped thin ferromagnetic layer.

In addition, an antireflective layer of Mg F₂(n=1.38) was formed on theback side of the substrate by vacuum evaporation with a thickness ofapproximately 100 nanometers, whereby constituting a magneto-opticaldevice of the present invention. With this antireflective layer, thelight reflectivity of the device in the visible region was reduced byabout 3%.

The optical characteristics of the striped thin ferromagnetic layer wassubsequently measured. Assuming s- and p-components of polarized lightto have the plane of its electric vector perpendicular and parallel tothe surface plane of the ferromagnetic layer, respectively, the stripedthin ferromagnetic layer plane was found to have intensity transmissioncoefficients at wavelength of 600 nanometers, of equal to or greaterthan 50% for s-component and equal to or less than 4% for p-component.From these values presently measured, the degree of polarization(T₁−T₂)/(T₁+T₂) at 600 nanometers was obtained as 86%, which isindicative of possible use of the striped thin ferromagnetic layer in apolarizing unit as well.

Portions of the striped thin ferromagnetic layer were magnetized by, forexample, drawing characters with a thin bar magnet of approximately 1 mmin diameter, on the side of the coated antireflective layer of thegrooved substrate. The ferromagnetic layer was subsequently placedbetween a pair of polarizing films and observed visually. As a result, adark appearance of the magnetized portions were observed, whichcorresponds to the rotation of the plane of linearly polarized light bythe Faraday effect upon the passage through the ferromagnetic layer andresultant shading of the light by the polarizing films. By contrast, noshading was observed for non-magnetized portions without the influenceof the Faraday rotation effect. Accordingly, characters previouslywritten into the ferromagnetic layer were found clearly legible with asatisfactory contrast.

Furthermore, another magneto-optical device was prepared in a similarmanner as above with the exception that a layer of aluminum was providedas a light reflecting layer in place of one of the polarizing layers onthe side of the substrate on which the ferromagnetic layer along thegrooves was formed.

When the portions of the striped thin ferromagnetic layer weresubsequently magnetized by drawing characters with a thin bar magnet ina similar manner as above, the characters were found clearly legiblewith a satisfactory contrast under light reflected from the lightreflecting layer.

EXAMPLE 2

A magneto-optical device was fabricated by repeating the procedure ofExample 1 with the exception that a magnetic oxide layer was disposed bysputtering a Bi₂Gd Fe₄AlO₁₂ target on the grooved quartz substrateheated at approximately 300° C. to a thickness of 57 nanometers on thehorizontal faces of the grooved substrate, in place of the iron particlelayer formed by the evaporation method of Example 1.

The thus disposed magnetic oxide layer was subjected to annealingprocess step at 650° C. for 3 hours. When the magnetic characteristicsof the magnetic oxide layer was measured, the value of the coerciveforce of 540 Oe was obtained on flat portions of the layer.

A layer of Ge was then disposed by sputtering on the grooved side of thequartz substrate to a thickness of 8 nanometers without heating thesubstrate at a pressure of 6.7×10 Torr and with an input power of 200 W.Subsequently, the portions of the Ge layer on horizontal faces of thegrooved substrate were removed by the reversed biased sputtering in asimilar manner to Example 1.

When the portions of the magnetic oxide layer were subsequentlymagnetized by drawing characters with a thin bar magnet and observedvisually in a similar manner as Example 1 described earlier, thecharacters were found clearly legible with a satisfactory contrast.

By contrast, when another device was prepared in similar manner as aboveexcept the Ge layer, no characters were found legible.

EXAMPLE 3

An array of micro magnetic heads as shown in FIGS. 5a and 5b wasprepared as follows. The array included a plurality of the micromagnetic heads 13 provided in a matrix on a 0.5 micron thick siliconwafer through the photolithography techniques.

Each of the micro magnetic heads 13 comprised of an FeNi disk-shapedmagnet 14 of 60 micron in diameter, which was provided in the centralportion of the head and surrounded by silicon portions 15, having aseven-turn coil of Au 17, which was wound around the tip portion of themagnet 14 and was embedded in polyimide resin 16.

A plurality of the thus constructed micro magnetic heads were arrangedin a lattice with a distance of 120 microns to thereby constitute thearray of micro magnetic heads.

The thus prepared micro magnetic head array was then provided on theanti-reflective layer of the magneto-optical device fabricated inExample 1.

The portions of the thin ferromagnetic layer of the magneto-opticaldevice were then magnetized by controlling current supplied to each ofthe micro magnetic heads to thereby write characters in theferromagnetic layer.

The magneto-optical device was subsequently placed between a pair ofpolarizing films and observed visually. As a result, a dark appearanceof the magnetized portions were observed, which corresponds to therotation of the plane of linearly polarized light by the Faraday effectupon the passage through the ferromagnetic layer and resultant shadingof the light by the polarizing films. By contrast, no shading wasobserved for non-magnetized portions without the influence of theFaraday rotation effect. Accordingly, characters previously written intothe ferromagnetic layer were found clearly legible with a satisfactorycontrast.

For the magneto-optical device fabricated as above, writing anddisplaying image information utilizing the ferromagnetic layer havebecome feasible as described earlier, by simply controlling the currentsupplied to each micro magnetic head without any translation ordisplacement of the magnetic head array relative to the magneto-opticaldevice.

In addition, by carrying out the writing and displaying imageinformation consecutively, displaying visually moving picture images isalso feasible by the device.

Furthermore, reading magnetic images is also feasible with thesimultaneous use of an ac magnetization coil and a dc detection coil, asdescribed earlier.

Comparative Example 1

A continuous, or not particulate, ferromagnetic layer of iron wasdisposed on a flat surface of quartz substrate to a thickness of 67nanometers by evaporation method. The transmission coefficient of thelayer in the visible region was found to be equal to or less than 40%,resulting visually in a dark appearance and no legible display images.

Comparative Example 2

A couple of continues magnetic oxide layers were disposed on a flatsurface of a 1 mm thick quartz substrate by sputtering in similar mannerto Example 2, one to a thickness of 100 nanometers and other to 900nanometers. Both layers were found to have a yellowish appearance,having transmission coefficients of approximately 80% in red spectralregion, whereas 30% or less in the region 500 nanometers or less.

The portions of the thus prepared magnetic oxide layer were subsequentlymagnetized by drawing characters with a thin bar magnet and placedbetween a pair of conventional polarizing films to be observed visually.

As a result, no image was found legible for the 100 nanometers thickmagnetic oxide layer. In addition, for the 900 nanometers thick layer,although images were legible in the transmission mode, no image wasobserved in the reflection mode (or the device construction with areflecting layer provided on one of the surfaces of the substrate).

Advantages of the Invention

According to claims 1 and 2 one aspect of the present invention, themagneto-optical device of the present invention includes a substratewhich is preferably transparent in the visible spectral region and aplurality of thin layers of ferromagnetic material disposed thereon,each of the thin layers preferably having a width of from 5 to 100nanometers and a thickness of from 0.1 to 5 microns, and being parallelwith one another with a spacing of from 0.2 to 2 microns.

The magneto-optical device is, therefore, capable of achieving both highlight transmittance and refractivity by magneto-optical effect at thesame time, to thereby result in a high contrast in transmittance valuesof visible light between magnetized and non-magnetized portions, whichis satisfactory for large area display panels. In addition, since themagneto-optical device has also an excellent response characteristics tothe intensity of applied magnetic field, the device is capable ofvisually displaying even slight differences in display contrast causedby minute differences in applied magnetic field strengths.

The magneto-optical device of claim 4 according to another aspect of thepresent invention is provided with a light reflecting layer. Themagneto-optical device is therefore capable of exhibiting an excellentcontrast in transmittance of visible light between magnetized ornon-transmittable portions of, and non-magnetized or transmittableportions of the device, to be used in a reflection type display.

The magneto-optical device of claim 5 according to still another aspectof the present invention is provided further with an anti-reflectionlayer. The light transmittance of the device is increased, to therebydisplaying picture images with a higher contrast.

The magneto-optical device of claim 6 according to another aspect of theclaimed invention is fabricated so as for its ferromagnetic layer to beelectrically conductive. The ferromagnetic layer of the device istherefore composed of the ferromagnetic layer by itself, having both ofthe polarization and magnetization capabilities, without providing anyadditional layer otherwise necessitated to gives rise to the electrontransfer in the layer.

The ferromagnetic layer of the magneto-optical device of claim 7 yetanother aspect of the present invention is composed of ultra-fineparticles of materials such as Fe, Co, Ni and alloys thereof, whichexhibit relatively large Faraday effects. The device, therefore, has ahigh transmittance as well as the large Faraday effect, and pictureimages of high contrast may be displayed by the device.

According to claim 8 a further aspect of the present invention, when aferromagnetic layer of the magneto-optical device is non-conductive, theferromagnetic layer is superimposed with non-magnetic semiconductor ormetal layers. The non-conductive ferromagnetic layer is thereforeprovided with polarization characteristics, thereby for the layer to beformed having both of the polarization and magnetization capabilities.

Description of the Reference Numeral

-   1 A substrate which is transparent in the visible spectral region.-   2 A side wall of concave grooves.-   3 A plurality of liner grooves provided in parallel with one    another.-   4 A thin layer of ferromagnetic material.-   4A A thin layer of ferromagnetic oxide.-   4X A magnetized portion of the thin layer of ferromagnetic oxide.-   4Y A non-magnetized portion of the thin layer of ferromagnetic    oxide.-   5 A polarization and magnetization layer.-   6 A light reflecting layer.-   7 An anti-reflection layer.-   8 A non-magnetic semiconductor or metal layer.-   9 A photoresist layer.-   10 Ar ions.-   11A Circularly polarized light.-   11B A light beam after passing through a magnetized portion 4X of    the thin layer of ferromagnetic material.-   11C A light beam reflected by a reflecting layer.-   12A Circularly polarized light.-   12B A light beam after passing through a non-magnetized portion 4Y    of thin layer of ferromagnetic material.-   12C A light beam reflected by a reflecting layer.-   13 A micro magnetic head.-   14 A disk-shaped magnet.-   15 A silicon portion.-   16 Polyimide resin.-   17 A coil.-   18 A terminal.-   19 A wiring.-   20 A two-dimensional array of micro magnetic heads.-   21 A magneto-optical device.-   22 A address circuit.-   23 A driver circuit.-   24 A controller.-   25 An external memory.-   26 Communication.-   27 A CPU.-   28 A memory.-   29 A magnetoresistance layer.-   30 A wiring.-   31 A substrate.-   32 A one-dimensional array of micro magnetic heads.-   33 A motor.-   34 A decoder.

1. A magneto-optical device comprising: a substrate transparent to lightin a visible spectral region; a plurality of ferromagnetic layers havinga width in an inclusive range of 5 through 100 nanometers and athickness in an inclusive range of 0.1 through 5 microns; wherein saidferromagnetic layers are parallel to each other and separated by adistance in an inclusive range of 0.2 through 2 microns.
 2. Themagneto-optical device of claim 1, wherein said substrate definesgrooves having side walls, said ferromagnetic layers being arranged onsaid side walls.
 3. The magneto-optical device of claim 2, wherein saidside walls are perpendicular to a surface of said substrate.
 4. Themagneto-optical device of claim 1, further comprising a reflecting layeron a first face of said substrate.
 5. The magneto-optical device ofclaim 4, further comprising an anti-reflecting layer on a second face ofsaid substrate.
 6. The magneto-optical device of claim 1, wherein saidferromagnetic layers are electrically conductive.
 7. The magneto-opticaldevice of claim 6, wherein said ferromagnetic layers comprise particlesof a member of the group consisting of Fe, Co, Ni, FeCo alloys, FeNialloys and CoNi alloys.
 8. The magneto-optical device of claim 7,wherein said ferromagnetic layers particles have an average diameter inan inclusive range of 2 through 20 nanometers.
 9. The magneto-opticaldevice of claim 1, further comprising a layer of non-magneticsemiconducting material or metal in contact with said ferromagneticlayers and having a same thickness as the thickness of the ferromagneticlayers and a width in an inclusive range of 5 through 10 nanometers. 10.The magneto-optical device of claim 2, further comprising a reflectinglayer on a first face of said substrate.
 11. The magneto-optical deviceof claim 10, further comprising an anti-reflecting layer on a secondface of said substrate.
 12. The magneto-optical device of claim 2,wherein said ferromagnetic layers are electrically conductive.
 13. Themagneto-optical device of claim 12, wherein said ferromagnetic layerscomprise particles of a member of the group consisting of Fe, Co, Ni,FeCo alloys, FeNi alloys and CoNi alloys.
 14. The magneto-optical deviceof claim 13, wherein said ferromagnetic layers particles have an averagediameter in an inclusive range of 2 through 20 nanometers.
 15. Themagneto-optical device of claim 2, further comprising a layer ofnon-magnetic semiconducting material or metal in contact with saidferromagnetic layers and having a same thickness as the thickness of theferromagnetic layers and a width in an inclusive range of 5 through 10nanometers.
 16. The magneto-optical device of claim 3, furthercomprising a reflecting layer on a first face of said substrate.
 17. Themagneto-optical device of claim 16, further comprising ananti-reflecting layer on a second face of said substrate.
 18. Themagneto-optical device of claim 3, wherein said ferromagnetic layers areelectrically conductive.
 19. The magneto-optical device of claim 18,wherein said ferromagnetic layers comprise particles of a member of thegroup consisting of Fe, Co, Ni, FeCo alloys, FeNi alloys and CoNialloys.
 20. The magneto-optical device of claim 19, wherein saidferromagnetic layers particles have an average diameter in an inclusiverange of 2 through 20 nanometers.
 21. The magneto-optical device ofclaim 3, further comprising a layer of non-magnetic semiconductingmaterial or metal in contact with said ferromagnetic layers and having asame thickness as the thickness of the ferromagnetic layers and a widthin an inclusive range of 5 through 10 nanometers.
 22. A magneto-opticaldevice comprising: a substrate transparent to light in a visiblespectral region; and a plurality of ferromagnetic layers having a widthin an inclusive range of 5 through 100 nanometers and a thickness in aninclusive range of 0.1 through 5 microns; wherein said ferromagneticlayers are parallel to each other.
 23. The magneto-optical device ofclaim 22, wherein said substrate defines grooves having side walls, saidferromagnetic layers being arranged on said side walls.
 24. Themagneto-optical device of claim 23, wherein said side walls areperpendicular to a surface of said substrate.
 25. The magneto-opticaldevice of claim 22, further comprising a reflecting layer on a firstface of said substrate.
 26. The magneto-optical device of claim 25,further comprising an anti-reflecting layer on a second face of saidsubstrate.
 27. The magneto-optical device of claim 22, wherein saidferromagnetic layers are electrically conductive.
 28. Themagneto-optical device of claim 27, wherein said ferromagnetic layerscomprise particles of a member of the group consisting of Fe, Co, Ni,FeCo alloys, FeNi alloys and CoNi alloys.
 29. A recording devicecomprising: a magneto-optical device comprising: a substrate, and aplurality of ferromagnetic layers on said substrate; and a magneticrecording head, on which said magneto-optical device is positioned,wherein said magnetic recording head comprises a plurality of bars ofmagnetic material.
 30. The recording device of claim 29, wherein saidmagnetic recording head further comprises lines wound around said barsof magnetic material.
 31. The recording device of claim 30, wherein saidbars of magnetic material are arranged in a matrix.
 32. An image formingapparatus comprising: an array of magnetic heads; and a magneto-opticaldevice on said array and comprising: a substrate, and a plurality offerromagnetic layers formed on said substrate, wherein a relativeposition between the magneto-optical device and the magnetic heads doesnot change during a recording operation.
 33. The image forming apparatusof claim 32, wherein said ferromagnetic layers have a width in aninclusive range of 5 through 100 nanometers.
 34. The image formingapparatus of claim 32, wherein said ferromagnetic layers have athickness in an inclusive range of 0.1 through 5 microns.
 35. The imageforming apparatus of claim 32, wherein said ferromagnetic layers areparallel to each other.
 36. The image forming apparatus of claim 35,wherein said ferromagnetic layers are separated by a distance in aninclusive range of 0.2 through 2 microns.
 37. The image formingapparatus of claim 32, wherein said substrate defines grooves havingside walls, said ferromagnetic layers being arranged on said side walls.38. The image forming apparatus of claim 37, wherein said side walls areperpendicular to a surface of said substrate.
 39. The image formingapparatus of claim 32, wherein said ferromagnetic layers are formed by amethod selected from the group consisting of sputtering, PVD, CVD andplating.
 40. The image forming apparatus of claim 32, furthercomprising: an address circuit configured to select a line of said arrayof magnetic heads; and a driver circuit configured to input and eraseinformation data to each head on the selected line.
 41. The imageforming apparatus of claim 40, further comprising a controllerconfigured to control writing and erasing operations of said informationdata.
 42. The magneto-optical device of claim 32, wherein each magnetichead of said array of magnetic heads includes a micro magnetic head anda reading head.
 43. The image forming apparatus of claim 42, whereinsaid reading head comprises a magnetoresistance film.
 44. The recordingdevice of claim 41, wherein each of said ferromagnetic layers ispositioned on a wall of said grooves.
 45. The recording device of claim44, wherein said ferromagnetic layers are separated from each other. 46.The recording device of claim 45, wherein said ferromagnetic layers areparallel to each other.